Arthur francis berry



A. F. BERRY.

TREATMENT OF MAGNETIC MATERIAL.

APPLICATION FILED JUNE 25 1918.

1,320,309. Patented Oct. 28,1919.

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ARTHUR FRANCIS BERRY, OF LONDON, ENGLAND.

TREATMENT OF MAGNETIC MATERIAL.

Specification of Letters Patent.-

ratentea oct. 28, rare.

Application filed June 25, 1918. Serial No. 241,754.

To all whom it may concern:

Be it known that I, ARTHUR FRANCIS BERRY, a subject of the King of GreatBritain and Ireland, residing at London, England, have inventedImprovements in or Belating to Treatment of Magnetic Material, of whichthe following is a specification.

This invention has for its object to improve the magnetic properties ofmagnetic material, such for example as iron produced by the open hearth,pneumatic or other metallurgical process, or electrolytically, and alsoiron alloys, compositions or the like, as for example iron-siliconalloys, so as to reduce' the hysteresis loss that takes place in suchmaterial during its use in alternating current apparatus, and also toincrease the magnetic permeability or electrical resistance, or both thepermeability and the resistance, of such material and thus to rendersuch material better adapted for use in apparatus of the kind referredto, particularly static transformers, than the magnetic materialsheretofore commonly employed.

With this object in View it has been proposed to subject magneticmaterial while in a heated condition to a magnetizing force bysurrounding it with a coil of Wire that is insulated from the magneticmaterial and, through which a continuous or alternating electric currentiscaused to pass, the magnetic material forming a core to the coil andbeing magnetized by the current passing through the coil.

The present invention has reference to improvements in the treatment ofmagnetic material whereby such material is better enabled to assume thephysical condition necessary for enhancing in a high degree thedesirable characteristics which magnetic material designed for use inalternating current apparatus should possess.

For this purpose according to the invention, magnetic material issubjected while in a heated condition, to the magnetizing anddemagnetizing action of alternating electric current while confined inan air tight chamber wherein a vacuum'is maintained, as by a vacuumpump, so that the material is relieved practically from all externalpressure and its particles or molecules thereby better enabled to movealternately in opposite directions in response to the alternatingmagnetizing and demagnetizing action produced by the alternating currentto which the material is subjected. This treatment of the magneticmaterial is or may be maintained during the heating up of the materialand also during the cooling thereof.

In this way the magnetic material is rendered less dense than ordinarymagnetic material and much less dense than such material that has beenput under great pressure while in a molten condition, as has sometimesbeen done.

The invention can be carried into practice in various Ways as will nowbe described with the aid of the accompanying illustrative drawingswherein Figures 1, 2, 3 and l are views showing partly in longitudinalsection and partly in elevation and .diagrammatically, differentarrangements of apparatus for the purpose.

1 is a vacuum chamber closed at its end by air tight covers 2 andadapted to contain the magnetic material 2 to be treated. 3 isa heatingchamber in which the vacuum chamber. is supported and through whichgases at a sufficiently high temperature to heat the interior of thevacuum chamber and its contents to the desired temperature, say up to atemperature of the order of about 750 to 800 0., can be caused to flow,4 and 5 being inlet and outlet passages respectively for the hot gases.6 is a vacuum pump connected to the Vacuum chamber 1 and whereby avacuum or partial vacuum can be set up therein. 7 is a coil of wireconnected to an alternate current generator 8 whereby an alternatingelectric current can be caused to flow through the coil 7 for thepurpose of subjecting the magnetic material 2 to an alternatingmagnetizing and demagnetizing force. 9 is a switch by which the electriccircuit can be closed and opened at will. The coil 7 may be insulated inany suitable manner to prevent its convolutions being short circuitedand, when necessary, to protect it against the action of the hot gases.

The alternating current may, as shown in Fig. 1, be passed through acoil 7 sur rounding the material 2 within the vacuum chamber 1, the coilbeing within the chamber with the magnetic material, but insulatedtherefrom. Or, as shown in Fig. 2, the

coil may be outside the vacuum chamber 1.

In each case the vacuum chamber may be of tubular shape the better toenable it to Withstand the external air pressure.

Or the heated magnetic material 2 may, as shown in Fig. 3, be subjectedto the mag netizing and demagnetizing force by including it in amagnetic circuit formed partly byan external magnetic core 10 betweenthe poles of which the magneticmaterial 2 is placed and which issubjected to such a force at a part thereof situated away from theheated portion of the magnetic material 2 as for instance by a coil 7surrounding such part traversed by an alternating current. In this casethe material 2 extends in an air tight manner through the end walls 2 ofthe vacuum chamber 1.

The alternating current passing through the coil in each case can be ofconstant or varying strength and of constant or variable periodicity andbe caused to pass through the coil either continuously or intermittentlyso that the material will be subjected to an alternating magnetizing anddemagnetizing force of constant or variable value and either constantlyor intermittently.

The magnetic treatment may advantageously be carried out while thematerial is heated to a high temperature within its limits of magneticsusceptibility, up say to the order of about 7 50 0., and also duringthe cooling of the material.

The magnetic material may be treated as described preferably While inthe form of sheets, strips, bars or the like, as may be desired, andaccording to the particular purpose for which it is to be used. Or itmay be in the form of billets or ingots.

The magnetic treatmentdescribed may be carried out during the ordinaryannealing treatment of the magnetic material,- and, it may be, aftersuch material has been rolled to the desired thickness and shape. foruse.

In some cases an electric current, either direct or alternating, may, asshown in Fig. 4, be passed through the heated magnetic material while itis being subjected to the magnetizing and demagnetizing force, thecurrent being supplied from a suitable electric generator 11 through aconductor 12 in electric connection with the magnetic material 2.

The magnetic treatment hereinbefore described may advantageously beapplied to magnetic material of various kinds including, in particular,magnetic material that has previously been remelted under vacuum, in aknown way, with a view to improving its magnetic properties.

Magnetically treated sheet magnetic material produced as hereinbeforedescribed may, previous to use in electrical apparatus and for thepurpose of further improv-- ing its value for such use, be grooved, orgrooved and insulated as and for the purpose described in thespecification of my British Letters Patent 1126-19. Such material afterbeing so grooved and insulated may be reheated to a high temperature,say of the order of about 750 (1, and magdemagnetizin force whileconfined in a heated condition within a chamber in which a vacuum 1smaintained during the magnetic treatment, substantially as and for thepurpose described. I

2. In carrying out the treatment referred to in claim 1, including 'theheated magnetic material in a magnetic circuit.

3. In carrying out the treatment referred to in claim 1, including theheated magnetic material in a magnetic circuit that is subjected to analternating magnetizing and demagnetizing force as a part thereof awayfrom the heated portion of the magnetic material, substantially asdescribed.

- 4:. In carrying out the treatment of magnetic material according toclaim 1, applying an electric current, either direct or alternating, tothe heated magnetic material while it is being subjected to thealternating magnetizing and demagnetizing force, substantially asdescribed.

5. In the manufacture of magnetic material, subjecting magnetic materialwhich has previously beenremelted under a vacuum, and while in a heatedsolid condition 1 and in a vacuum, to an alternating ma netizing anddemagnetizing treatment, su stantially as described. I

6. In the treatment of magnetic material, subjecting such material whilein the form of sheets to an alternating magnetizing and demagnetizingforce while confined in a heated condition in a vacuum, afterwardgrooving the sheets as set forth and afterward subjecting the groovedsheets while in a heated condition and in a vacuum, to alternatingmagnetizing and demagnetizing force, substantially as described.

7. For carrying out the treatment referred to in the claim 1, a vacuumchamber to contain the magnetic material to be treated, a vacuum pumpfor producing a vacuum in the said chamber, a coil surrounding butinsulated from the magnetic material under treatment and means forcausing altern-atin current to pass through the coil, substantially asdescribed.

Signed at London, England this 5 day .of June 1918.

ARTHUR FRANCIS BERRY.

